Bacteria

Classification of Bacteria

Bacteria and blue-green algae are prokaryotes—that is, they are organisms that lack membranes surrounding their genetic material. Today most scientists place prokaryotes in the kingdom Monera. Formerly, bacteria and blue-green algae were considered to be primitive plants and were classified in the plant kingdom.

Bacteria are generally classified by two methods. The simplest and oldest method is by shape. The three principal categories are:

Bacilli

(singular: Bacillus), rod-shaped bacteria; the most numerous of all types. They include coccobacilli and streptobacilli.

Cocci

(singular: Coccus), spherical bacteria. This group is divided into bacteria that occur in pairs, such as the diplococci; in clusters, such as the staphylococci; and in chains, such as the streptococci.

Every species on Earth, from the majestic humpback whale to the bacteria happily living in your gut, has a special role to play within a defined ecosystem. Can organisms ever trade their existing niches for new ones?

Imagine a time in Earth's far-flung past when organisms didn't swim through the oceans or populate the lands. Even the mighty dinosaurs hadn't arisen. Will the planet ever return to that lifeless state?